Gobetwino (go between o) is listening on the serial port, for "commands coming from Arduino, and in response it will do something for Arduino and possibly return something to Arduino.
Gobetwino defines a set of command types that can be used as templates to create actual commands. Arduino can ask Gobetwino to execute these commands, and return something to Arduino.
So what can Gobetwino do? Using the defined command types you can create commands in Gobetwino that Arduino can ask Gobetwino to execute. These commands can:
Start a program on the PC.
Start a program, and wait until it finishes, and tell Arduino it finished.
Send data to any windows program from Arduino, like it was typed on the keyboard.
Send email, optionally with an attached file.
Download a file from the internet.
Read a file and return data to Arduino.
Log data from Arduino to a file, with an optional timestamp.
Periodically check a POP3 mailbox for incoming mails and send commands from the mail to Arduino.
Get the time from the PC.
Get the date from the PC.
Ping a host or IP address.
Copy a file on the PC.
With combinations of these commands you can do things like:
Start any program on your PC, either directly or via an associated file type.
Start Excel, send data from Arduino directly into the Excel sheet, save the sheet and email it, without touching your PC.
Send e-mails to a POP3 mailbox and have Arduino react to the contents of the emails.
Log data directly to a CSV file on the PC, so the data can be used in spreadsheets or databases.
Download a file from the internet and have Arduino ask for a specific line of data from the file.